You can’t really tell.
It’s also a very very VERY small platform compared to other social media platforms like Reddit. (I had another comment where I calculated this but it’s ridiculously small)
It is unlikely that it would see anywhere near the same level of dedicated bot activity due to the low return on invested effort.
This is a problem that will become greater once the value of astroturfing and shifting opinion on Lemmy is high enough.
This does nothing the data is record kept and mass deleting/shredding your comments is already deductible and there have already been cases where shredded comments have been reversed after people have deleted their account.